Which statements about the compound shown are correct? Count as alpha hydrogens those on carbons directly bonded to a carbonyl carbon. Select all that apply.

AThe OCH $_{2}$ hydrogens of the ethyl group are alpha hydrogens of the ester carbonyl.
BThe CH $_{2}$ hydrogens between the two carbonyl groups are the most acidic.
CThere are 5 alpha hydrogens in total.
DIt exists as an equilibrium of keto and enol forms, and the enol is stabilised by conjugation and an intramolecular hydrogen bond.

Answer: B, C, D

The compound shown is ethyl acetoacetate. The alpha hydrogens are the 3 H of the acetyl CH

_{3}

and the 2 H of the central CH

_{2}

, a total of 5; the CH

_{2}

is flanked by two carbonyls and is the most acidic. The OCH

_{2}

carbon is bonded to oxygen, not to the carbonyl carbon, so its hydrogens are not alpha hydrogens. The enol form is stabilised by C=C-C=O conjugation and a six-membered hydrogen-bonded ring.

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Which statements about the compound shown are correct? Count as alpha hydrogens those on carbons directly bonded to a carbonyl carbon. Select all that apply.

Answer: B, C, D

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